As disclosed in U.S. Pat. No. 3,408,671, the compound N,N-diethyl 2(.alpha.-naphthoxy)propionamide has been found to be a useful herbicide. The above patent describes a method of preparation of this herbicide wherein .alpha.-naphthol is reacted with N,N-diethyl-.alpha.-bromopropionamide in the presence of a 25% solution of sodium methoxide in methanol.
An alternative route for the manufacture of the above herbicide is described in co-pending application Ser. No. 604,968. Pursuant to the latter, diethylamine is reacted with an .alpha.-halopropionic acid in the presence of phosphoryl chloride, to produce an N,N-diethyl-.alpha.-halopropionamide, which is in turn reacted with .alpha.-naphthol in the presence of an alkali metal hydroxide, to form the desired product. An undesirable aspect of this process is the production of phosphoric acid wastes and the problem of their disposal.
A third alternative utilizes the same intermediate, N,N-diethyl-.alpha.-chloropropionamide, but arrives at this intermediate by reacting diethylamine with .alpha.-chloropropionyl chloride in the presence of an excess of an aqueous solution of an alkali metal hydroxide. The production of phosphoric acid wastes is avoided. This type of reaction is disclosed in U.S. Pat. No. 3,914,302.
The compound .alpha.-chloropropionyl chloride is a known compound which can be manufactured by a variety of techniques, examples of which are as follows: reaction of .alpha.-chloropropionic acid with phosgene in the presence of dimethyl formamide catalyst; the reaction of .alpha.-chloropropionic acid with thionyl chloride [Leimu, Ber. 70, 1049 (1937)]; the reaction of propionic acid with SO.sub.2 Cl.sub.2 and I.sub.2, or with SO.sub.2 Cl.sub.2 and benzoyl peroxide in carbon tetrachloride [Kharasch et al., J. Am. Chem. Soc. 62, 927-928 (1940)]; the reaction of propionyl chloride with chlorine and iodine [Wolfenstein et al., Ber. 41, 735 (1908); Michael, Ber. 34, 4035, 4037 (1901)]; and the reaction of (CH.sub.3 CHOHCO.sub.2).sub.2 Ca with PCl [Wurtz, Ann. 107, 194 (1858)].
Starting materials for the above reactions are either expensive or obtainable through a series of additional reactions which are costly to run and provide less than stoichiometric yield. The object of the present invention is to provide a process for the manufacture of .alpha.-chloropropionyl chloride from an alternate starting material, 1,2-dichloropropane, in a three-step process. Use of 1,2-dichloropropane as a starting material will be advantageous when this compound can be obtained more cheaply than other starting materials. Its use will be further advantageous in commercial plants where by-products of the chlorination of this compound (the first step of the process of the present invention as described more fully hereinbelow) can be used as feed for the manufacture of perchloroethylene and carbon tetrachloride.
Another object of the present invention is to provide a process for the manufacture of .alpha.-chloropropionyl chloride from 1,1-dichloropropene-1 in a one-step process.